A new experimental Alzheimer’s drug, solanezumab, developed by Eli Lilly has raised hopes for a breakthrough in the treatment of the disease. The progress was reported at the Alzheimer’s Association International Conference in Washington DC, USA, based on an extension of a previous phase III trial that failed to prove the efficacy of solanezumab when it ended in 2012.

While the trial was declared a failure, reports said a close reading of the data revealed a 34% slowdown in the rate of mental decline among more than 1,000 people with mild Alzheimer’s. Patients in this category were allowed to continue taking the drug for a further two years and those who had previously been given a placebo were switched to solanezumab.

Eli Lilly said the benefit gained by patients taking the drug during the trial compared with people on placebo was maintained during the two-year extension period, suggesting that the change in the course of the disease was long-lasting rather than temporary.

The company said a new analytical method enabled it to assess whether solanezumab had an effect that is consistent with slowing progression of disease by modifying the underlying disease progression, which until now had not been studied.

 “The results provide encouraging evidence that solanezumab could indeed be acting on the disease processes that drive Alzheimer’s,” said Eric Karran, research director at Alzheimer’s Research UK, the charity.

Solanezumab is counted among the most advanced of several drugs in development that aim to reduce the build-up of beta-amyloid that form plaques in the brain. Up to now, most treatments could provide only temporary relief of symptoms without being able to slow progression.

More than 120 Alzheimer’s drugs have failed in clinical trials since 1998. In one of the latest, Roche stopped one late-stage study of its gantenerumab last December because it didn't meet its main goal of a cognitive benefit in people with early Alzheimer's symptoms.

Researchers believe, however, that Lilly’s positive data will add to cautious optimism that a corner has been turned. Biogen in March of this year announced positive results from a small, first-stage study of another amyloid-reducing medicine, aducanumab.

An effective treatment for Alzheimer’s is considered one of the most urgent public healthcare priorities as an aging world population threatens to increase the number of people with the disease from an estimated 44 million today to 76 million by 2030.